540 kHz LPF

With the aid of the the WA4DSY filter calculator, a 5-pole Chebyshev filter was constructed. The capacitors are 3 kV ceramic type, 3n3+3n3+1n=7.6 nF for the two ends (C1, C3) and 10n+3n3=13.3nF for the middle capacitori (C2).

The coils were constructed with 32 mm PVC tubing and 27 turns of 22 AWG ECW. The performance of the filter is acceptable, with less than 1 dB insertion loss, at least 30 dB attenuation at 1 MHz and at least 60 dB attenuation at 2 MHz.

With this filter attached to the output of the transmitter, the first harmonic is measured to be less than -60 dBc.